1. Field of the Invention
The present invention relates to an information writing and reading apparatus using an information recording medium having a plurality of sectors and, more particularly, to an information writing and reading apparatus which can prevent error operation caused by inconsistent management data stored in DMAs (Defect Management Areas).
2. Description of the Prior Art
Recently, an information writing/reading apparatus uses large capacity and interchangeable recording medium, such as an optical disk. Especially, an optical disk apparatus uses laser and forms tiny pits on the optical disk to write data on the disk. Therefore, the optical disk is very suitable for writing large capacity and interchangeable information. Since the optical disk is interchangeable, the optical disk is provided with a plurality of DMAs (Defect Management Areas), each storing the disk management information. The disk management information stored in the DMAs are exactly the same for the purpose of fail-safe. Each DMA has DDS (Disk Definition Structure) to specify the structure of the disk and a defect list information.
In FIG. 1, a user area of a 90 mm rewritable optical disk is shown. The disk is provided with four DMAs: DMA1 and DMA2 are positioned at the inner periphery of the disk; and DMA3 and DMA4 are positioned at the outer periphery of the disk. Four DMAs carry the same information from the viewpoint of fail-safe. If DMA1 is determined as unreliable, DMA2 is detected, and if DMA2 is unreliable, DMA3 is detected, and so on. The rewritable area is located between the inner periphery DMA2 and the outer periphery DMA3. Each DMA has one sector of DDS, a plurality of sectors of PDL (Primary Defect List) and a plurality of sectors of SDL (Secondary defect List).
In FIG. 2a, data construction of the DDS data is shown. The DDS has an identification code to indicate that this sector is the DDS, a partition information for the rewritable area, a PDL pointer indicating the address from which the PDL area starts, and an SDL pointer indicating the address form which the SDL area starts.
In FIG. 2b, data construction of the PDL data is shown. The PDL has an identification code to indicate that the following sectors are the PDL, a PDL list length of data indicating the list length of the following PDL list, and a PDL list listing the addresses of primary defect sectors. In the PDL list, one entry occupies four bytes for storing an address of a defect sector.
In FIG. 2c, data construction of the SDL data is shown. The SDL has an identification code to indicate that the following sectors are the SDL, an SDL list length of data indicating the list length of the following SDL list, and an SDL list listing the addresses of secondary defect sectors together with addresses of substitute sectors where the data is to be replaced. In the SDL list, one entry occupies eight bytes for storing an address of a defect sector and an address of a replaced sector.
The DDS and the PDL are recorded only at an initialization processing of the disk. The SDL is rewritten and recorded when the disk is initialized, and the defect sector is detected during the writing/reading processing of the data in the rewritable area without initialization. The DMA area of a 90 mm rewritable optical disk is specified in ISO/SC23 WG2 CD10090.
Generally, the format operation is done during the initialization of a disk. During the format operation, the DDS, the PDL which is stored with the defect sector detected at the certification (disk supervisory), and the SDL which has no entry of the defect sector are stored in the DMA area. Depending on the type of format, the certification processing is omitted, resulting in a blank PDL, storing no defect sector in the PDL area or eliminating the PDL itself.
The start up operation is done after the reset or insertion of a disk, and is to read the disk management information including the defect management information sent from the DMA area in the disk in order to initiate the writing and reading processing of the data for use in the disk.
The SDL updating process is to add new entries in the SDL to the disk, and is done after a new defect sector was detected during each reading or writing on a rewritable area on the disk.
However, the conventional information writing and reading apparatus has a problem such that the plurality of DMAs (DMA1, DMA2, DMA3 and DMA4), which should be completely identical to each other, may not be identical due to the presence of a defect sector in the DMA area or unexpected power failure during the formatting or updating of the defect list. Therefore, the conventional information writing and reading apparatus has a problem that when there is a discrepancy among the information stored in DMAs, the area management or the defect sector management can not be carried out properly.